From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56237C3A59F for ; Thu, 29 Aug 2019 19:45:21 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D01CE2166E for ; Thu, 29 Aug 2019 19:45:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D01CE2166E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 46KCkh69xvzDr6d for ; Fri, 30 Aug 2019 05:45:16 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=suse.de (client-ip=195.135.220.15; helo=mx1.suse.de; envelope-from=msuchanek@suse.de; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=suse.de Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 46KChX5ztpzDs09 for ; Fri, 30 Aug 2019 05:43:24 +1000 (AEST) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 1CF54ABE7; Thu, 29 Aug 2019 19:43:21 +0000 (UTC) Date: Thu, 29 Aug 2019 21:43:19 +0200 From: Michal =?UTF-8?B?U3VjaMOhbmVr?= To: Arnd Bergmann Subject: Re: [PATCH v4 1/4] powerpc: make llseek 32bit-only. Message-ID: <20190829214319.498c7de2@naga> In-Reply-To: References: <061a0de2042156669303f95526ec13476bf490c7.1567072270.git.msuchanek@suse.de> <20190829143716.6e41b10e@naga> <20190829161923.101ff3eb@kitsune.suse.cz> X-Mailer: Claws Mail 3.17.4 (GTK+ 2.24.32; x86_64-suse-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michael Neuling , "Eric W. Biederman" , Nicolai Stange , David Hildenbrand , Greg Kroah-Hartman , Heiko Carstens , Linux Kernel Mailing List , Nicholas Piggin , David Howells , Hari Bathini , Geert Uytterhoeven , Allison Randal , Andrew Donnellan , Firoz Khan , Breno Leitao , Paul Mackerras , Thomas Gleixner , linuxppc-dev , Christian Brauner , Joel Stanley Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, 29 Aug 2019 16:32:50 +0200 Arnd Bergmann wrote: > On Thu, Aug 29, 2019 at 4:19 PM Michal Such=C3=A1nek = wrote: > > On Thu, 29 Aug 2019 14:57:39 +0200 Arnd Bergmann wrote:= =20 > > > On Thu, Aug 29, 2019 at 2:37 PM Michal Such=C3=A1nek wrote: =20 > > > > On Thu, 29 Aug 2019 14:19:46 +0200 Arnd Bergmann wr= ote: =20 > > > > > On Thu, Aug 29, 2019 at 12:23 PM Michal Suchanek wrote: > > > > > In particular, I don't see why you single out llseek here, but le= ave other > > > > > syscalls that are not needed on 64-bit machines such as pread64()= . =20 > > > > > > > > Because llseek is not built in fs/ when building 64bit only causing= a > > > > link error. > > > > > > > > I initially posted patch to build it always but it was pointed out = it > > > > is not needed, and the interface does not make sense on 64bit, and > > > > that platforms that don't have it on 64bit now don't want that usel= ess > > > > code. =20 > > > > > > Ok, please put that into the changeset description then. > > > > > > I looked at uses of __NR__llseek in debian code search and > > > found this one: > > > > > > https://codesearch.debian.net/show?file=3Dumview_0.8.2-1.2%2Fxmview%2= Fum_mmap.c&line=3D328 > > > > > > It looks like this application will try to use llseek instead of lseek > > > when built against kernel headers that define __NR_llseek. > > > =20 > > > > The available documentation says this syscall is for 32bit only so > > using it on 64bit is undefined. The interface is not well-defined in > > that case either. =20 >=20 > That's generally not how it works. If there is an existing application > that relies on the behavior of the system call interface, we should not > change it in a way that breaks the application, regardless of what the > documentation says. Presumably nobody cares about umview on > powerpc64, but there might be other applications doing the same > thing. Actually the umview headers go out of their way to define the llseek syscall as invalid on x86_64 so that the non-llseek path is taken.=20 mview-os/xmview/defs_x86_64_um.h:#define __NR__llseek __NR_doesnotexist It is probably an oversight that this is not done on non-x86. I am not even sure this builds on non-x86 out of the box. > It looks like sparc64 and parisc64 do the same thing as powerpc64, > and provide llseek() calls that may or may not be used by > applications. And if they are supposed to build with !compat it should be removed there as well. >=20 > I think your original approach of always building sys_llseek on > powerpc64 is the safe choice here. That's safe but adds junk to the kernel as pointed out in the reply to that patch. Thanks Michal